Circuit arrangement for a peltier module

ABSTRACT

A circuit arrangement for a Peltier module for use in a Peltier heat pump for a tumble dryer with the circuit arrangement including a Peltier module having at least one series arrangement of Peltier elements, with each series arrangement of Peltier elements being configured to receive voltage; and a two-position transfer switch wherein at a first position voltage is applied to the Peltier module and at a second position voltage is not applied to the Peltier module and the Peltier module is connected to another electrical device.

The invention relates to a circuit arrangement for a Peltier module for use in a Peltier heat pump for a tumble dryer, with the Peltier module including at least one series arrangement composed of Peltier elements and each series arrangement being capable of having a direct voltage applied to it.

A Peltier element in terms of design and function is known from a document which was downloadable from the internet address http://de.wikipedia.org/wiki/Petier-Element on Nov. 25, 2005, said Peltier element having the previously described design. The half elements of this Peltier element are pillar- or block-shaped and consist of doped semiconductors as materials. The semiconductors are in particular bismuth telluride and p-conductively doped and n-conductively doped semiconductors are used. A half element consisting of the p-conductively doped semi conductor and a half element consisting of the n-conductively doped semiconductor are each connected to one another on one side by way of a printed circuit board, also known as a metal bridge and on another side, which is opposite to the said side, by way of an additional printed circuit board in each instance having an additional half element or a terminal contact in order to connect the Peltier element to an electrical network.

Further details with regard to the basics, user-related selection and assembly of Peltier elements may be derived from the documents which were downloadable from the internet addresses http://www.guick-ohm.de/waerme/download/Erlaeuterung-zu-Peltierelemen.pdf and http://www.quick-ohm.de/waerme/download/Einbau.pdf on Nov. 25, 2005.

DE 1410 206 A discloses a washing machine, in which laundry can not only be washed but also dried. The publication indicates several alternatives for the additional apparatuses required herefor; in particular provision can be made for an electrical heating device for heating an air flow used to dry laundry and for a simple heat exchanger for cooling down the heated air flow once the laundry has been loaded, the heater and the cooling system can however also form part of a heat pump apparatus. The heat pump apparatus may be a heat pump apparatus which operates with Peltier elements in order to utilize the thermoelectric effect.

A device emanating from an English extract belonging to JP 08 057 194 A in the data collection “Patent Abstracts of Japan” for drying laundry, which in turn corresponds to the version described in the introduction, contains in its first channel system, in addition to a heater and a cooling system, which both form part of a thermoelectrically operable heat pump apparatus, an additional heat exchanger which is arranged upstream of the cooling system for cooling the air flow dissipated from the laundry and an additional heating apparatus arranged downstream of the heater for additionally heating the air flow before loading the laundry.

It is the object of the invention to make use of the properties of the Peltier module during operation in the most simple and effective way possible, particularly with regards to solving the problem of a monitoring the function of the Peltier module and the tumble dryer, in which the Peltier module is integrated, in as simple and effective a way as possible.

The object is achieved by a circuit arrangement for a Peltier module for use in a Peltier heat pump for a tumble dryer, with the Peltier module including at least one series arrangement composed of Peltier elements and with each series arrangement being capable of having a direct voltage applied to it, with a transfer switch with two positions being provided in accordance with the invention, in the first position of which the direct voltage is applied to the Peltier module and in the second position of which the direct voltage is not applied to the Peltier module, but the Peltier module is instead connected to another consumer.

The invention particularly addresses the Seeback effect occurring in the Peltier module which is separated from each voltage supply as a reversal of the thermoelectric effect in order to optionally supply suitable other consumers and also renders possible the use of specific electrical characteristics and measured variables.

The transfer switch allows for the fact that another consumer in the tumble dryer can use an electrical voltage, which occurs as a result of the Seeback effect, if the Peltier module is exposed to a temperature difference between the assigned heater and the assigned cooling system without being connected to an external electric voltage. The transfer switch can be controlled by a control unit of the tumble dryer. Here the control unit can at least optionally control the transfer switch as a function of a temperature on the Peltier module or another suitable location in the tumble dryer and thus periodically repeatedly implement corresponding measurements. As a result, it is possible to introduce a regulation function, within the scope of which the Peltier module is switched off if the temperature leaves a critical range. The regulating temperature is dependent on the temperature sensor data and the dimensioning of the control circuit.

The other consumer preferably includes an interior illumination of the tumble dryer. Such an interior illumination is then primarily important if the tumble dryer is open for loading or unloading and thus does not necessarily need to be operated simultaneously with the Peltier module.

Further preferred consumers, which can be connected to the Peltier module as an alternative to the voltage supply, are sensors and controllers for suitable aspects of the processes and display elements running in the tumble dryer. Such an additional consumer is further preferably integrated into a control unit for the tumble dryer.

The other consumer particularly preferably includes a sensor for a voltage obtained via the Peltier module. Because this voltage, generated by the Seeback effect, depends on the temperature difference present via the Peltier module, it is possible to determine this temperature difference, particularly for use as an input variable to control the drying process running in the tumble dryer, by measuring this voltage.

The other consumer likewise preferably includes a sensor for an electrical resistor of the Peltier module. As a result of the highly negative temperature coefficients of a conventional Peltier element, a measurement of the operating temperature of the Peltier module is possible by way of measuring the electrical resistance, with the operating temperature being an excellent and preferred measured variable for identifying a malfunction in the dryer.

The direct voltage for supplying the Peltier module is preferably generated by rectification of the mains voltage, in particular a 230 Volt alternating current, in a mains rectifier. The number of Peltier elements and the manufacturer of the Peltier elements are selected such that they are optimally matched to this rectified mains voltage. In other words, the number of Peltier elements and the manufacturer are selected such that the Peltier elements of the series arrangement are operated by having the rectified mains voltage applied to the series arrangement at an operating point, which is at least suited and preferably optimized to the use of the Peltier module in a Peltier heat pump. The Peltier module is thus directly operated using mains voltage. This represents a particularly simple manner of providing a rectified voltage, especially within the scope of a tumble dryer connected to the mains voltage.

It is not necessary for the control unit to control the so-called transfer switch in order to regulate the temperature. Instead, a switch can also be controlled, which can interrupt the entire voltage supply, because it is arranged for instance on the alternating current side of the mains rectifier and can interrupt the alternating current supply. This then allows for the fact that in the meantime, the other consumers do not require the voltage during the temperature regulation of the Peltier module, so that the rectifier can be completely switched off during the course of the regulation process.

The temperature control of the said type is used to regulate the temperature within a certain range. An excess-temperature protection system can also be provided. This can be configured considerably more directly than is of the case with the intermediate path of a special temperature sensor. A thermal switch can be directly thermally coupled to the Peltier module. If the Peltier module (at the coupling point) exceeds a certain temperature, the thermal switch switches. The thermal switch can be arranged on the direct current side, it is however preferably arranged on the alternating current supply side to the mains rectifier, so that it completely interrupts the alternating current supply in the event of an excess temperature.

In order to stabilize the rectified voltage of the mains rectifier, a buffer capacitor can be arranged downstream of the mains rectifier on the direct current side. The charge current on the buffer capacitor is preferably limited by a charge current limiter (NTC type for instance).

The corresponding interconnection logically results in that the buffer capacitor is connected in parallel to two outputs of the mains rectifier and that the charge current limiter is arranged in the current path between a terminal of the mains rectifier and a terminal of the buffer capacitor.

As the circuit arrangement in an electrical device (tumble dryer) is to be marketed for use by means of any end consumer and this device is subjected to corresponding legal regulations, a choke is to be arranged on the alternating current side of the mains rectifier to serve for power factor correction (PFC choke) in order to fulfill these regulations in respect of a possible mains feedback.

A preferred embodiment of the invention is described below with reference to the drawing, with the FIG. illustrating the circuit diagram of the inventive circuit arrangement.

FIG. shows a schematic representation of a Peltier module 1, which is to be used in a Peltier heat pump for a tumble dryer. The Peltier module includes Peltier elements 2 connected in series, with twelve Peltier elements 2 being shown here, though the Peltier module need not be confined to the number twelve. In contrast: the number of Peltier elements 2 and the operating values of the Peltier elements 2 (i.e. the manufacturer of the Peltier elements 2) are mutually configured such that the series arrangement of the Peltier elements 2 can be operated with a voltage which results with the rectification of the mains voltage. A Peltier module 1 with more than one series arrangement as shown here is also conceivable, with the individual series arrangements usually being arranged in parallel to one another.

The mains voltage of 230 volt alternating current (230 Vac) is firstly provided to generate the rectified mains voltage, with the terminals L and N being shown schematically here. The alternating voltage is rectified by a mains rectifier 3, which has a conventional design of a rectifier. A buffer capacitor 4 is provided in order to stabilize the rectified voltage, said buffer capacitor being connected in parallel with terminals of the mains rectifier 3 on the direct current side. A load current limiter 5 (NTC resistor, i.e. resistor with a negative temperature coefficient) is located in the switched path from the one terminal of the mains rectifier 3 to the one terminal of the buffer capacitor 4.

A thermal switch 6 which automatically switches in the case of a corresponding temperature change is thermally coupled to the Peltier module 1. In the case of excess-temperature of the Peltier module 1, the thermal switch 6 switches to the alternating current side of the mains rectifier 3, interrupts the alternating voltage supply and thus switches off the Peltier module 1.

The temperature regulator can also be designed to be somewhat more accurate. A temperature sensor 7 is provided for this at a predefined point on the Peltier module 1. This supplies electronic measured values to a control unit 111 controlling the tumble dryer in order to correspondingly control a relay control circuit (shown as a transistor circuit). A switch 9 on the alternating current side can likewise be actuated by way of the relay control circuit, i.e. the entire Peltier module 1 can be switched off. The relay control circuit 11 has a direct voltage signal from the control unit 11 of the tumble dryer as an additional input. The Peltier module 1 can thus also be indirectly switched off by means of a corresponding relay control circuit and the switch 9.

A transfer switch 10 (relay) is also provided. The rectified mains voltage can similarly be separated from the Peltier module 1 with the aid of the transfer switch 10. Here however the rectifier 3 still remains active and the direct voltage is correspondingly available. After separation from the direct voltage, the Peltier module 1 is connected to an interior illumination 12 of the tumble dryer. Four light-emitting diodes and an additional resistor which is connected in series to the light-emitting diodes are shown schematically here for the interior illumination 12. Another consumer which is integrated into the control unit and is symbolized in the drawing is connected in parallel with the interior illumination. This other consumer may be an additional sensor, a controller, a display element or a plurality of such additional consumers. An additional consumer in the form of a voltage or resistance measuring apparatus can be periodically repeatedly connected to the Peltier module 1 by transferring the transfer switch in order to obtain measured values for controlling a drying process running in the tumble dryer.

The transfer switch 10 is likewise controlled by way of the relay control circuit 11, but can if necessary be regulated as a function of the temperature measured by the temperature sensor 7. The transfer process separates the Peltier module 1 from the direct voltage, as a result of which the temperature falls again. If the temperature measured by the temperature sensor 7 drops below a certain limit value, the control unit 11 is active again and reverses the switch 10 so that the Peltier module 1 is again connected to the rectified mains voltage.

In order to fulfill legal requirements in respect of the mains feedback of the circuit arrangement, a choke 8 for power factor correction (PFC) is arranged upstream of the rectifier 3.

The Peltier module 1 has operating values which are optimized by suitably selecting the number of individual Peltier elements and by suitably selecting the type thereof such that it can be operated with a rectified mains voltage. In other words, the operating point is optimized when the rectified mains voltage is provided in order to operate the Peltier module 1 for use within the scope of a Peltier heat pump.

An excess-temperature protection system is provided by means of the thermal switch 6. Automatic temperature regulation is enabled with the aid of the temperature sensor 7 and the switch 9 and/or 10, which are controlled by the control unit 11. 

1-14. (canceled)
 15. A circuit arrangement for a Peltier module for use in a Peltier heat pump for a tumble dryer, the circuit arrangement comprising a Peltier module including at least one series arrangement of Peltier elements, with each series arrangement of Peltier elements being configured to receive voltage; and a two-position transfer switch wherein at a first position voltage is applied to the Peltier module and at a second position voltage is not applied to the Peltier module and the Peltier module is connected to another electrical device.
 16. The circuit arrangement according to claim 15 wherein the electrical device includes at least one interior illumination lamp disposed within the tumble dryer.
 17. The circuit arrangement according to claim 15 wherein the electrical device is operatively connected to a second electrical device including one of a sensor, a controller and a display element.
 18. The circuit arrangement according to claim 17 wherein the electrical device is integrated in a control unit for the tumble dryer.
 19. The circuit arrangement according to claim 17 wherein the electrical device includes a voltage sensor directed to sensing voltage obtained via the Peltier module.
 20. The circuit arrangement according to claim 17 wherein the electrical device includes a sensor for an electrical resistor of the Peltier module.
 21. The circuit arrangement according to claim 17 and further comprising a temperature sensor attached to the Peltier module, said temperature sensor being connected to a control unit wherein a temperature of the Peltier module is detectable with said temperature sensor.
 22. The circuit arrangement according to claim 21 wherein the control unit is configured to control the transfer switch based on a temperature detected by the temperature sensor.
 23. The circuit arrangement according to claim 21 wherein the control unit is configured to control a switch for selectively interrupting the main voltage supply.
 24. The circuit arrangement according to claim 23 wherein the switch is operationally connected to the AC side of the main voltage rectifier for interrupting the AC supply voltage.
 25. The circuit arrangement according to claim 17 wherein a thermal switch is thermally coupled to the Peltier module for interrupting the AC supply to the main voltage rectifier when a specific temperature of the Peltier module is exceeded.
 26. The circuit arrangement according to claim 17 wherein a buffer capacitor is operationally disposed downstream of the main voltage rectifier on a DC side in order to stabilize the rectified DC voltage, wherein a charge current on the buffer capacitor is limited by a charge current limiter in operational communication therewith.
 27. The circuit arrangement according to claim 17 wherein an inductor for power factor correction is operationally disposed upstream of the main voltage rectifier on an AC side.
 28. The circuit arrangement according to claim 17 wherein DC voltage is produced in a main voltage rectifier by rectifying the main voltage and wherein the Peltier elements of the series arrangement are operated by applying the rectified main voltage to the series arrangement at an operating point configured for use of the Peltier module in a Peltier heat pump. 